Mechanical performance of composite materials developed using novel re-entrant star auxetic fibrous architectures

In this research, novel high performance auxetic fabric structures (and composites) were produced using the flat knitting technology and their auxetic and tensile behaviors were characterized. The fabrics were produced using two types of high performance fibres (para-aramid and polyamide) and by varying the structural and process parameters. Subsequently, the produced fabrics were impregnated with an epoxy resin using the vacuum infusion technique to produce composite materials. It was observed that all fabrics and composites produced based on the re-entrant star design were auxetic in nature, though the negative Poisson ratio (NPR) was much higher in case of the auxetic fabrics than the composites. The maximum NPR obtained in the wale and course directions for fabrics and composites were -0.5 and - 0.32, and -0.17 and -0.20, respectively. Overall, all auxetic fabrics and composites showed a superior strength and energy absorption capability as compared to their non-auxetic counterparts, except the polyamide auxetic composites, which showed a lower strength than the non-auxetic composites.